The present invention relates to the pouring of molten metal from teeming vessels. More particularly, it relates to valve apparatus for controlling the flow of molten metal from a teeming vessel into a receiver, such as, for example, the mold of a continuous caster.
In U.S. Pat. No. Re. 27,237, granted Nov. 23, 1971 to J. T. Shapland, there is described a valve apparatus for controlling the flow of metal from a bottom-pour vessel. The described valve incorporates refractory plates that are adapted to be moved in sequence into an operative position beneath the pour opening of the vessel. The plates utilized are either blank, imperforate members operative to prevent the flow of metal from the vessel or contain orifice openings sized to control the rate of metal teemed from the vessel. Flow regulation is achieved in such valve by selectively moving plates containing different diameter orifice openings in sequence into their operative position beneath the vessel pour opening.
Teeming valves of the described type are beneficial in that plate change is rapidly effected such that metal flow can be promptly terminated in the case of the development of a hazaradous condition. The valves are also beneficial in that changes in flow conditions for regulation purposes can be achieved in a minimum of time. Such valves, however, suffer from the disadvantages that the rate of flow through the valve can be regulated only by replacing the operative slide plate with one having an orifice opening of different diameter, thus precluding the ability to vary flow rates over an infinitely variable range. The need to change plates in order to alter metal flow conditions also renders the use of such prior art valves costly in that the number of plates utilized over a period of valve operation is increased and a large number of plates containing orifice openings of different diameters must be inventoried.
Infinitely variable metal teeming valves are not new as evidenced by U.S. Pat. Nos. 3,436,023, 3,454,201 and 3,866,806. However, none of these valves have the ability to maintain the flow throttling function of the valve completely independent of the emergency shutoff function. Accordingly, not only is rapid response to an unsafe condition requiring termination of flow unattainable with their use but also immediate return of flow to the regulated flow rate upon reinstatement of teeming is impossible.
It is to the solution of these and other problems attendant with the use of prior art metal teeming valves that the present invention is directed.